This invention relates to methods and systems for determining whether containers have apertures or leaks by trying to create a vacuum in the containers.
Prior art systems and methods for determining whether a container has an aperture or leak generally include a means for pressurizing a container and a means for measuring the ability of the container to maintain a pressure. More particularly, these systems and methods may include either a star wheel system or a conveyor system for moving containers. These systems and methods may also include a compressor or other device for directing the flow of a pressurized fluid into the container, and a measuring device for measuring the pressure inside the container once it is filled with pressurized fluid. In most applications, the pressurized fluid is air. After determining the pressure inside of the container, the measuring device typically communicates with a controller for determining whether the pressure of the fluid in the container exceeds a predetermined value. If the pressure of the interior of the container exceeds a predetermined value, this indicates that the pressurized fluid has been retained in the container and that the container does not have an aperture. Conversely, if the pressure of the inside of the container is below the predetermined value, this indicates that the container has an aperture or leak.
As an alternative to detecting leaks with compressed air, systems and methods for detecting leaks in a container by determining whether a container can hold a vacuum have also been developed. Similar to the pressurized air systems, the vacuum type systems draw a vacuum in the container and then test the ability of the container to maintain a vacuum. If a container cannot hold a vacuum, this indicates that it has a leak, and conversely if a container can hold a vacuum, this indicates that the container does not have a leak. Examples of such systems are disclosed in U.S. Pat. No. 3,762,213 (Nowicki) and U.S. Pat. No. 5,025,657 (Schenk). Nowicki teaches that a vacuum can be created in a container by moving a cam driven diaphragm that is attached to the top of a container that is riding on a conveyor belt. Assuming that a container does not have a leak, a vacuum is created within the container, as the diaphragm moves. If a vacuum is created in the container, the system of Nowicki raises the container off of the belt for a predetermined period of time and this indicates that the container does not have a leak. However, if the system is unable to hold the container for the predetermined of time in a raised position, this indicates that the container cannot hold a vacuum and has a leak. Similarly, Schenk teaches evacuating a container with a vacuum pump and then applying a pressure to the exterior of the container to determine whether the container can maintain a vacuum. If the container maintains a vacuum, this indicates that the container does not have a leak, and if the container does not maintain a vacuum this indicates that the container does have a leak.
As described above, a variety of pressurized air and vacuum systems for detecting the presence of a leak in a container have been developed. Many of these systems cover the top of a container with a port through which pressurized air can be directed into the container or a vacuum can be drawn in the container. Typically, this port is sealed to the top of the container. A pressure detector is generally placed in communication with the port to measure the pressure or vacuum within the container. The pressure or vacuum in the container may be measured after a predetermined period of time. This measured pressure or vacuum is compared to a predetermined pressure that a container having no leaks should have after it has been pressurized or depressurized for the predetermined period of time. If the container maintains the pressure or the vacuum for the predetermined period of time, this indicates that the container does not have a leak. Conversely, if the container is unable to maintain the requisite pressure for a predetermined period of time, this indicates that the container has a leak.
This invention relates to improved systems and methods for detecting leaks in containers. This invention also relates to improved systems and methods for detecting leaks in containers by determining if a vacuum can be created within a container.